Populations of Paracentrotus lividus have been widely studied across their geographic range due to their key role as herbivores capable of transforming benthic communities. However, no comprehensive population assessment had previously been conducted in the Canary Islands. We carried out an extensive survey between 2006 and 2009 across five islands and the northern islets of Lanzarote, sampling both intertidal and subtidal habitats. Sea urchin abundance, algal composition, and physical variables were recorded to identify spatial patterns in population distribution. Macroalgal assemblages were grouped into functional categories: turf, Lobophora, brown erect algae, red bushy algae, and crustose corallines. Lobophora showed a strong negative relationship with P. lividus abundance, whereas brown erect algae were associated with the highest sea urchin densities. Island identity emerged as a major structuring factor, particularly in the subtidal, revealing a clear archipelagic gradient: populations were nearly absent in the westernmost island (El Hierro) and progressively more abundant toward the eastern islands. Wave exposure also significantly influenced abundance and size structure, although effects differed between habitats. In subtidal zones, P. lividus was more abundant in exposed areas, whereas intertidal densities peaked at intermediate exposure levels. At smaller spatial scales, substrates characterized by higher structural complexity and porosity supported greater sea urchin abundance. By integrating environmental drivers across spatial scales, this study highlights the combined influence of habitat structure, algal composition, and hydrodynamic conditions in shaping P. lividus distribution, providing a baseline for future management and conservation strategies in oceanic island systems.

Sea cucumber fisheries have continued to expand during the past decade at a fast rate, despite the predictable drop during the COVID-19 period. The exploitations are now qualified as ‘serial’ and ‘contagious’. The most recent trends are shown through the analysis of Food and Agriculture Organization’s capture data, collected from different countries and territories. The mean captures per year, in fresh weight, are over 90.103 tonnes. The mean trade data for years 2019–2021 are given by category of commodities, which complicates the trade analysis. The imports, in quantity and value, show the usual importance of China and Hong Kong, and now of Saudi Arabia. The exports show the importance of the frozen products from Canada. The statistics from Hong Kong in quantities and values (for imports and re-exports) are analysed for the past decade. Globally, catches have increased in comparison to previous studies, with new countries and territories developing export fisheries, new species targeted from new regions, and new products traded. The continued growth and expansion of the global sea cucumber trade is alarming as the sustainability of many species-specific fisheries remains of great concern. Stronger conservation measures, and their implementation, at national, regional, and international levels, are required to effectively protect biodiversity, promote sustainable resource use, and address the escalating impacts of the increasing exploitation efforts.

This study reports the first record of Caprella moradi Momtazi, Sari & Darvish, 2020 from India. The specimens for this study were collected from Diu and Veraval coast of Gujarat State, India. Caprella moradi can be identified by the presence of four rows of small setae on body surface, curved anterior margin of male gnathopod 2 propodus and unequal size of gills 3 and 4. Caprella moradi can be differentiated from its close congener Caprella danilevskii; Czerniavski, 1868 by these consistent morphological characters. Examination of materials collected from Gujarat and their comparison with published figures indicates that the previous report of C. danilevskii from India actually corresponds to C. moradi.

Marine tardigrades are known from all oceans. However, Euclavarctinae (Halechiniscidae) is the only family-group taxon exclusive to the deep sea. We describe a new genus and species of this taxon, Ranarctus kondoi gen. et sp. nov. The new genus and species was sorted from a sediment sample collected at a locality north of Kuroshima island, Kerama Islands, Okinawa, Japan (water depth: 596–606 m) during a T/RV Toyoshiomaru cruise (Hiroshima University) in 2003. It does not completely conform to the subfamily’s diagnosis as in the case of Parmursa by its aliform expansions, trapezoid head, and primary clava and lateral cirrus sharing a common pedestal. Aside from these similarities, Ranarctus gen. nov. differs from Parmursa by its wrinkled aliform expansions lacking ribs, cephalic cirri’s constant-width scapi, and internal digits longer than external ones.

ZooBank LSID: urn:lsid:zoobank.org:pub:F096F6D5-0A25-4E99-8258-767550931186.

Mussel cells from three age groups (i.e., 2–4, 5–6, and ≥ 10 years) were tested for lysosomal membrane stability (LMS – membrane permeability and proton pump function), autophagic rate, and intralysosomal reactive oxygen species (ROS). LMS was significantly reduced in haemocytes and digestive cells of the hepatopancreas (digestive gland) in the two older groups of mussels, while autophagy in haemocytes was reduced in the oldest age group. ROS generation was measured in digestive cells and was reduced in the oldest age group. Age-related decline in LMS and autophagy may be related to dysfunction of the PI3P-Akt-mTOR signalling pathway. Lysosomal autophagy can also be a source of ROS generation as the degradation product lipofuscin (age/stress pigment) accumulates in autolysosomes and residual bodies; and lipofuscin-associated iron can generate ROS. Previous investigation found age-related increased lipid peroxidation in digestive gland cells, whereas this study only assessed ROS generation in the lysosomal compartment of digestive cells and may reflect increased lysosomal and autophagic dysfunction. Principal component analysis, multidimensional scaling, and cluster analysis showed that the three age groups were significantly different from each other, with the oldest mussels showing the greatest degree of cellular dysfunction. The anti-oxidative protective role of autophagy and possible links to lysosomal and autophagic dysfunction in ovarian oocytes and fecundity reduction with age are discussed in the context of increased fragility in health of older animals (e.g., digestion, autophagic recycling and repair & innate immunity). Consequently, it is recommended that young mussels should be used in environmental biomonitoring with LMS.

To date, there are no records of appendicularian assemblages or associated investigations in the waters adjacent to the Kuroshio Current around the Nansei Islands, Japan. In this study, plankton samplings were conducted with a North Pacific Standard net hauled vertically from a depth of 200 m to the surface to investigate the appendicularian community structure in such waters. Five species were newly recorded in the western North Pacific, each representing a new geographical record for the region. The new records include Fritillaria aequatorialis, Fritillaria pacifica, Fritillaria pellucida omani, Appendicularia tregouboffi, and Kowalevskia oceanica, which belong to appendicularian families Fritillariidae and Kowalevskiidae. Among them, F. aequatorialis, A. tregouboffi, and K. oceanica represent the first records in the entire Pacific Ocean. Owing to the under sampling of appendicularian assemblages in tropical and subtropical waters in the Pacific Ocean and a lack of systematic quantitative and qualitative research on this topic, these species might have been overlooked for a long time in Japanese waters.

The study confirms a significant biogeographic extension of the goby species Drombus key (Smith) in Indian waters from the Western Indian Ocean to the Northern Bay of Bengal based on nine specimens collected from the mudflat region of the Bahuda estuary, Odisha. The transitional zone of the Bahuda estuary represents an active interface between marine and freshwater systems. The transitional zone experiences extreme salinity fluxes for which some dominant ichthyofaunal assemblages occur like gobies. The species D. key has the unique character of a triangular yellow mark before a black blotch on the pectoral fin upper base. The species was earlier reported from East Africa to Seychelles and Madagascar, and the present study reported the species for the first time from the Indian coast. Additionally, the species D. key has no genetic data in prior studies and this study also adds four COI gene barcodes of the species, which will contribute towards the potential use of the barcode data library.

September 2024 marked the 20th anniversary of the commencement of operations of the Antarctic Treaty Secretariat. Despite the importance of this institutional milestone, it went largely unnoticed and sparked little critical reflection in Antarctic governance circles. This article seeks to fill that gap by assessing the Secretariat’s role, performance, and evolution within the Antarctic Treaty System as a whole. The article explores the Secretariat’s contributions to continuity, coordination, transparency, and institutional memory. It also examines the constraints the Secretariat faces due to its lack of international legal capacity, limited mandate and budget, and the political dynamics among the Consultative Parties. Finally, the article offers reflections on the Secretariat’s future role in a changing geopolitical and environmental landscape, arguing that strengthening its functions may be essential to ensuring the continued order and stability of the Antarctic region.

The paintpot cuttlefish Ascarosepion tullbergi (Appellöf, 1886) exhibits a distinctly benthic lifestyle, in contrast to the typical ontogenetic shift from benthic to nekto-benthic modes observed in most cuttlefish species. While many cuttlefish initially attach to substrates using arms IV and the ventral mantle, they generally transition to swimming-based locomotion as they mature. A. tullbergi, however, remains benthic throughout its life, relying on arms IV and the lateral edges of the ventral mantle for attachment and using an ambling gait for locomotion from hatching to adulthood. Despite the ecological significance of benthic specialisation, embryonic development in fully benthic cuttlefish remains poorly studied, as previous research has primarily focused on nekto-benthic species. To address this gap, we described the embryonic development of A. tullbergi and compared it with that of other sepiid species. Although the overall developmental pattern of A. tullbergi is broadly similar to that of other nekto-benthic cuttlefish, this species exhibits a pronounced early investment in benthic traits, particularly in the development of arms IV and the lateral edges of the mantle. Specifically, arms IV in A. tullbergi develop earlier and more prominently than in other Sepiidae species that undergo ontogenetic shifts in life mode. This early specialisation underscores the unique ecological strategy of A. tullbergi and reflects its adaptation to a lifelong benthic niche. The present study provides a description of embryonic development in A. tullbergi and contributes to a deeper understanding of cephalopod diversity.

A new species of spionid polychaete from the coastal waters of southwest India, Trochochaeta chakara sp. nov., is described and illustrated. Adults are common on Alappuzha mud banks (locally known as Chakara) off the coast of Kerala. They live in silty tubes in soft sediment and are characterized by the presence of two pairs of red eyes, caruncle extending to end of chaetiger 1, heavy falcate spines in neuropodia of chaetigers 2 and 3 (those in chaetiger 3 much stronger and darker), capillary chaetae in notopodia of chaetigers 1, 3–10, frayed heavy spines in neuropodia of chaetigers 4–13, hirsute capillaries in neuropodia from chaetiger 14, lateral interneuropodial membranes from chaetiger 14, one pair of ventral papillae on each chaetiger from chaetigers 14–16, bundles of acicular spines in notopodia from chaetigers 50–52, and small pygidium with up to six pairs of short cirri. This is the third species of Trochochaeta described and found in the Indian Ocean, including T. orissae (Fauvel, 1932) and T. cirrifera (Hartman, 1975).

A new sponge species (Demospongiae: Poecilosclerida: Podospongiidae) is described offshore from the Cape of Good Hope, on the southern edge of the Table Mountain National Park marine protected area. Podospongia capensis sp. nov. is compared to Podospongia natalensis, described by Kirkpatrick (1903) from the east coast of South Africa, as well as to all other Podospongia species described to date. The new species differs from P. natalensis in having a shorter, thicker stalk, lacking anisostrongyles as megascleres, and possessing a second category of large symmetrical aciculospinorhabds microcleres that are present in P. natalensis. Additionally, P. natalensis has larger oxeas and styles than those found in P. capensis sp. nov. Furthermore, the two species are geographically separated, with P. natalensis described from the Natal ecoregion, while P. capensis sp. nov. is described from the Southern Benguela ecoregion. The new species primarily differs from other congeners in external morphology and size of the oxeas and styles.

Portunid crabs of the genus Charybdis De Haan, 1833 are among the most frequently reported marine invaders worldwide. Here, we report the first record of Charybdis (Archias) hoplites (Wood-Mason, 1877) outside its native Indo-West Pacific range, collected from the Test Estuary, Southampton Water, United Kingdom. Morphological and molecular analyses confirm the specimen’s identity and clarify diagnostic features useful for distinguishing C. (A.) hoplites from closely related taxa. This represents the northernmost record of any Charybdis species and suggests a long-distance dispersal event, associated with shipping activities in the Port of Southampton. Environmental data indicate that salinity and turbidity at the collection site are within known tolerances for Charybdis spp., although low winter temperatures may limit survival and establishment. The detection of this warm-water species in a major international port highlights the ongoing need to monitor non-native marine fauna.

Studying social behaviour of mobile and cryptic marine mammals is challenging, particularly for small species like harbour porpoises whom in many areas tend to be challenging to initially spot and then gain repeated observations. Recently, there has been a rise in the number of observations of harbour porpoises occurring in atypical group sizes that are larger than the typical size of two to three individuals. This behaviour, in conjunction with the evolving availability and usability of Unmanned Aerial Vehicle (UAV) technology, is supporting and improving the capture of information on social behaviours. Around Shetland, Scotland, harbour porpoises are sighted from land via opportunistic and systematic surveys year-round with atypical group sizes also observed. To capture information on group size, opportunistic and systematically collected UAV footage were collated and analysed. This revealed sexual approach behaviours in typical group sizes of small groups (two to four individuals), as well as atypical group sizes of medium groups (five to nine individuals), large groups (10 to 19 individuals), and aggregations (≥20 individuals) occur in multiple bays around Shetland. This is the first insight into group sizes and behaviours for the region which was recently designated as an Important Marine Mammal Area (IMMA). Further insight into these social behaviours and group size (e.g. seasonality, site fidelity) could aid harbour porpoise conservation and management within the IMMA and elsewhere.

We investigated the epizoic diatoms colonizing the carapace of the spider crab Hyastenus hilgendorfi inhabiting Lake Timsah in the Suez Canal. A total of 63 individuals, free of macro-epibionts, were examined to assess the diversity, abundance, and seasonal dynamics of their associated diatom communities. A total of 61 diatom taxa belonging to 31 genera were recorded, with raphid pennate diatoms being the most dominant, particularly Navicula lanceolata. Diatom density and diversity exhibited clear seasonal variation, where Summer had the highest richness and Spring the highest cell densities. Overall, males hosted more diatom taxa than females, however, sex-specific differences fluctuated seasonally. The cluster analysis revealed distinct diatom assemblages between sexes and seasons, showing subtle but significant variation in epibiont structure. These findings provide the first detailed characterization of epizoic diatom assemblages on H. hilgendorfi. They suggest that seasonal variations in diatom communities may influence the crab’s camouflage effectiveness by altering biofilm characteristics which facilitate macro-epibiont settlement.

This study provides the first results on the population dynamics of Sphyraena sphyraena (Linnaeus, 1758) in the western Mediterranean. Otoliths and scales reading were used for its age and growth investigation in Eastern coast of Algeria. The monthly evolution in marginal increment data of scales and otoliths revealed that only one annulus is formed per year in February. Fish length and radii of the scales or otoliths were closely correlated. Both methods showed four age groups. ANOVA test (P < 0.05) revealed insignificant differences between both estimates of length at age results. Growth parameters estimated using length-at-age data from both methods confirming the age determination results. The total mortality (Z ), natural mortality (M ), and fishing mortality (F ) were estimated at 1.19 year−1, 0.826 year−1, and 0.363 year−1, respectively. The growth performance index (Ø ) was 2.57. The estimated exploitation ratio (E ) was 0.305. The length–weight relationship is EW = 0.0104 TL2.702, showed that the growth rates were negative allometric. The results revealed the compatibility of otoliths and scales reading for assessment studies of Sphyraena sphyraena .

Rare Earth Elements (REEs) are essential for green energy technologies and defense systems, yet global supply chains remain concentrated in China. This has intensified geopolitical competition for alternative sources, positioning the Arctic as a strategic frontier, as retreating ice exposes mineral deposits. A comprehensive discourse analysis of strategic documents, scholarly literature, and media sources from 2010 to 2025 reveals a dramatic shift from geological characterization and economic speculation to urgent securitization and strategic alliance formation. Academic research has evolved from establishing natural baselines to governance and social conflict analysis. Media coverage of REE in the Arctic peaked in 2025, with rising emphasis on governance, sovereignty, geopolitics, and Greenland’s strategic position. Critical gaps persist in addressing Indigenous rights, holistic impact assessments, and Arctic-specific innovation. Sustainable Arctic REE development requires integrated frameworks that balance geopolitical imperatives with environmental protection and Indigenous self-determination, preventing the region from becoming a sacrifice zone for global decarbonization.